D0 Half-Metallic Ferromagnetism in GeNaZ (Z = Ca, Sr, and Ba) Ternary Half-Heusler Alloys: an Ab initio Investigation

Abstract

First-principles approach based on density functional theory was applied to investigate the structural, elastic, phonon dynamics, thermodynamics, electronic, and magnetic properties of GeNaZ (where Z = Ca, Sr and Ba) ternary Heusler alloys. The Perdew-Burke-Ernzerhof generalized gradient approximation (GGA) and the modified Becke-Johnson (mBJ-GGA) were used for the exchange-correlation energy and potential. The GeNaZ ternary Heusler alloys were found to be half-metallic and stable in the ferromagnetic α phase. The alloys were found to satisfy the criteria for dynamic and elastic stabilities. Thus, they are dynamically and elastically stable. The calculated spin-polarized electronic band structure and density of states using GGA (mBJ-GGA) reveal that the minority spin channel has metallic character and the majority spin channel having an electronic band gap of 0.26 (0.59), 0.39 (0.66), and 0.08 (0.33) eV for the GeNaCa, GeNaSr, and GeNaBa ternary Heusler alloys, respectively. The considered alloys all result in a stable ferromagnetic half-metallic ground state structure with a magnetic moment of 1 μB/cell. The density of states and the spin-charge density of these alloys show that the magnetization originates primarily from the 4p states of the Ge atoms. The GeNaZ ternary Heusler alloys do not have any magnetic elements, and their induced magnetism makes them very promising materials for spintronic devices.